This invention relates to a group supervision apparatus for an elevator system wherein a service cage is selected from among a plurality of cages and is assigned to a hall call, and wherein a cage is caused to respond to a call or to stand by.
In a case where a plurality of cages are juxtaposed, a group supervision operation is usually performed. One type of group supervision operation is an assignment system. This system is such that, as soon as a hall call is registered, assignment estimation values are calculated for the respective cages, the cage of the best estimation value is selected and assigned as a cage to-serve, and only the assigned cage is caused to respond to the hall call, thereby to enhance service efficiency and to shorten hall wait time. In the group-supervisory elevator system based on such an assignment system, arrival pre-announcement lamps for the individual cages and individual directions are commonly installed at the hall of each floor, whereby the pre-announcement display of the assigned cage is presented to a user waiting at the hall. Therefore, the waiting user can wait for the cage in front of the pre-announcement display without anxiety.
The assignment estimation values in the system for assigning the cage to the hall calls as stated above are calculated on the basis that, assuming present circumstances to proceed as they are, which of the cages should optimally be assigned the hall call. More specifically, on the basis of cage positions and cage directions at present and hall calls and cage calls presently registered, there are obtained predictive values of the periods of time required for each cage to successively respond to the calls and arrive at the halls of the corresponding floors (hereinbelow, termed "arrival expectation times") and the periods of time having lapsed since the registrations of the hall calls (hereinbelow, termed "continuation times"). Further, the arrival expectation times and the corresponding continuation times are added to calculate the prediction wait times of all the hall calls presently registered. Besides, the summation of the prediction wait times or the summation of the squared values of the prediction wait times is set as the assignment estimation value, and the first-mentioned hall call is allotted to the cage whose assignment estimation value becomes the minimum. With such a prior-art system, in the case of allotting the hall call, whether or not the alloted cage is the optimal is determined according to the present circumstances. For this reason, there has occurred the drawback that a hall call registered anew after the allotment results in a long wait.
Examples of the occurrence of the drawback will be explained with reference to FIGS. 12-15. In FIG. 12, letters A and B designate Cage No. 1 and Cage No. 2, respectively, both of which are standing by under closed door states. It is assumed that, in such circumstances, down calls 7d and 6d are respectively registered in the 7th floor and 6th floor successively as illustrated in FIG. 13. According to the assignment estimation values of the prior-art assignment system, the down call 7d of the 7th floor is allotted to the cage A and the down call 6d of the 6th floor to the cage B so as to minimize the wait times as a whole. Thus, both the cages travel upwards, and then reverse their travelling directions in the 7th and 6th floors substantially at the same time.
Assuming that a down call is registered in any floor above the 7th floor, for example, in the 8th floor after the reversals of the directions, it becomes a rear call for the travelling directions of the cages A and B. Whichever cage may be assigned, the down call 8d of the 8th floor requires a long wait-time till a response thereto can be provided.
On the other hand, in a case where the down call 7d of the 7th floor is allotted to the cage A and where the down call 6d of the 6th floor is thereafter registered, this call is assumed to be also allotted to the cage A. Then, as illustrated in FIG. 14, even when the down call 8d of the 8th floor is simultaneously registered, the cage B standing by in the b 1l st floor does a direct travel service, and hence, the down call 8d does not become the long wait. In this manner, in order to prevent long waits, the hall calls need to be allotted so as to prevent the cages from gathering together in one place, considering how the cages will be arranged in the near future and even by temporarily performing an allotment which prolongs wait times.
With a so-called zone assignment system, in which a building is divided into a plurality of floor zones and in which cages are assigned to the respective zones so as to serve hall calls the hall calls are responded to as illustrated in FIG. 15, and the long wait of the down call 8d of the 8th floor is avoided. Since, however, the floors included in the respective zones are fixed, the down call 8d of the 8th floor results in a long wait as will be explained herebelow: By way of example, in a case where a down call from the 5th floor is registered, unlike the down call 6d from the 6th floor, the down calls of the 7th floor and 5th floor are separately allotted to the respective cages A and B without a response to the down call 8d of the 8th floor as in the case of FIG. 14. In this manner, the zone assignment system cannot flexibly cope with the registered situation of the hall calls, and it also has the problem that a long wait call arises.
In addition, the official gazette of Japanese Patent Application Publication No. 32625/1980 discloses an assignment system wherein, in order to prevent cages from gathering together in one place and to attain an enhanced service efficiency likewise to the zone assignment system, when a hall call is registered, the cage scheduled to stop in a floor near that of the call is assigned to the call. Even in this assignment system, merely note is taken of the presence of the cage which is scheduled to stop in the near floor, and a judgement is not made by accurately grasping the changes of cage arrangements with the lapse of time, such as how long the cage scheduled to stop takes to arrive at the floor, how other hall calls are distributed and registered and when they will possibly be responded to, and what floors the other cages lie in and which directions they will travel in. Accordingly, there is left the problem that long wait calls similarly arise.
Further, the official gazette of Japanese Patent Application No. 56076/1987 discloses, in an elevator system wherein cages are caused to stand by at positions where passengers have alighted from the cages, an assignment system in which when a hall call occurs anew, it is tentatively allotted to the respective cages in succession so as to expect the alighting positions of the tentative assignment cages, the degrees of dispersion of the cages are calculated from the expected alighting positions of the tentative assignment cages and the positions of the other cages, at least the degrees of dispersion are used as the estimation values of the respective cages, and an assignment cage is determined from the estimation values of the respective cages so that the cage exhibiting a higher degree of dispersion may be assigned more easily. Thus, the cages are dispersively arranged even after the end of the service to the hall call, and the wastefull operations of unoccupied cages ascribable to the dispersive standby are prevented, so that a great effect is demonstrated for saving energy. Another effect is that the disrust of the inhabitants of a building equipped with the elevator system can be eliminated. As apparent from its object, however, this assignment system is directed toward a time zone of light traffic such as the nighttime, and it is premised on a case where one hall call is registered in the state in which all the cages are standing by as the unoccupied cages. Therefore, this assignment system cannot be applied to the allotment of hall calls in such a traffic situation that the hall calls are successively registered and that the cages are respectively travelling while responding to the calls, and it has the problem that long waits arise. Such a problem is caused by the fact that, since the assignment system is intended to balance the arrangement of the unoccupied cages, it does not consider the changes of cage positions with the lapse of time for the cages other than each tentative assignment cage (in view of the premise, the assignment system need not consider the changes of the cage positions of the other cages), and the fact that the hall call allotment is judged by taking note only of the cage arrangement at the point of time at which the tentative assignment cage will be alighted from (at that point of time, all the cages will become unoccupied and fall into standby states).